(a) Field of the Invention
The present invention relates to signal transmission film, a control signal part and a liquid crystal display including the signal transmission film.
(b) Description of the Related Art
A liquid crystal display is one of the flat display devices widely used at the present time. The liquid crystal display comprises two substrates on which a plurality of electrodes are formed, a liquid crystal layer sandwiched between the two substrates and two polarizing films for polarizing the light attached to each outward surface of the substrates. The liquid crystal display controls the light transmittance, thereby to display picture images by applying different voltages to the electrodes while forming electric fields for varying the orientation of the liquid crystal molecules of the liquid crystal layer. In such a liquid crystal display, thin film transistors are formed in one of the two substrates, which is called as a TFT substrate, and switch the voltages applied to the electrodes.
A display region for displaying picture images is situated in the center of the TFT substrate. A plurality of signal lines, or a plurality of gate lines and data lines are formed in the directions of row and column, respectively. The gate lines and the data lines cross each other, thereby to define a plurality of pixel element regions. Each pixel element has a pixel electrode to which the data signal is applied via the data line. The thin film transistor sends the data signal transmitted via the data line to the pixel electrode by the gate signal transmitted via the gate line.
A plurality of gate pads connected to the gate lines and a plurality of data pads connected to the data lines are formed outside of the display region. These pads are connected to the external driving integrated circuits thereby to receive gate signals and data signals from the external driving integrated circuits and send them to the gate lines and the data lines.
A printed circuit board for gate signal transmission and a printed circuit board for data signal transmission are attached to the thin film transistor substrate using an anisotropic conducting film through an heat and compression process thereby to send the gate and the data signals to the thin film transistor. The thin film transistor and the printed circuit board for data signal transmission are connected by a data signal transmission film on which the data driving integrated circuit is mounted. The data driving integrated circuit converts an electric signal into a data signal and sends the data signal to the data line. And also, the thin film transistor and the printed circuit board for gate signal transmission are connected by a gate signal transmission film on which the gate driving integrated circuit is mounted. The gate driving integrated circuit converts an electric signal into a gate signal and sends the gate signal to the gate line.
Herein, gate control signals for controlling the gate signal could be outputted from the printed circuit board for data signal transmission not from the printed circuit board for gate signal transmission. And, these gate control signals could be transmitted to the gate signal transmission film.
The gate control signals are various kinds of control signals such as a gate-on-voltage, a gate-off-voltage and a common voltage for reference voltage to the difference of the data voltage in the thin film transistor.
These gate control signals inputted into the gate driving integrated circuit, while driving the liquid crystal display, have various kinds of magnitudes of voltage and are transmitted through gate control signal connection wires. The gate control signal connection wires are arranged abreast and closely on the thin film transistor substrate. Accordingly, a high voltage signal wire transmitting a high voltage such as the gate-on-voltage and a low voltage signal wire transmitting a low voltage such as the gate-off-voltage are arranged abreast and closely.
In this arrangement of the wires, a potential difference is formed between the high voltage signal wire and the low voltage signal wire while driving the liquid crystal display. However, this potential difference causes an electrolysis reaction with moistures permeated into the wires during manufacturing and operating the liquid crystal display, by a rule of the galvanic cell, thereby to damage the high voltage signal wire and results in inferior devices.